Tektronix 485 vs 2465B

[GeorgeOfTheJungle]

My favourite is the 2232, at the flip of a switch becomes a DSO and it's got plenty of knobs and buttons including four very handy direct save/recall waveform memories.

Edit: it's only 100 MHz though.

[David Hess]

The 2465 has a mesh accelerator anode so the focus isn't as good as on the 485 or the 7000 series crts. It's difficult to describe objectively but it's a feature of the 24xx scopes that I never liked. My personal preference would be 485.

The 485 and 7000 and practically anything newer than the last of the 500 series have scan expansion meshes.  The 2465 series, 7104, and the 11302 are the exception as they have box or quadrupole lenses to allow the use of microchannel plate image intensifiers.

But scan expansion is scan expansion whether from a scan expansion mesh or box lens so they all suffer from a larger spot size.  The only model I find it actually noticeable on is my 465 and the sharpest CRT I have is naturally from my 547 with my high acceleration voltage 7000 mainframes which should perform similar to a 485 being close behind and much brighter.  My 2445B might be my "fuzziest" except for my 465 but I suspect both would improve if I used them much like my 7603 improved; CRTs left in storage for years seem to become fuzzy until powered for a couple of days.

Does any of this matter for practical use?  It might if you have a choice.  Otherwise just recognize that high bandwidth oscilloscopes like the 485 have sharper and brighter CRTs than lower bandwidth oscilloscopes like the 465.

The 100MHz 22xx models which replaced the 100MHz 465/465B seem to have better CRTs but maybe the difference is just due to age; I have seen lots of different 22xx models over a long time but only a couple of 465s for a short time.

My favourite is the 2232, at the flip of a switch becomes a DSO and it's got plenty of knobs and buttons including four very handy direct save/recall waveform memories.

I really like the 2232 also.  With peak detection it covers storage applications just fine and the storage display looks much better than one would expect because of the high resolution of the CRT.

[G0HZU]

Does any of this matter for practical use? 

It definitely mattered for me in the 1980s when I was a student as I used the old Tek 585 to help me repair/service ham/CB SSB radios to supplement my student income. The two tone response on the 585 was a class apart from a 465 and I would have refused to use a 2465 for stuff like this because the trace is so unrewarding to look at and the detail at the waveform crossover would have been lost in fuzz and noise. But then again the 2465 was a new scope and cost a fortune back then. Even the oldest and scruffiest of the 465s in M&B radio in Leeds were several hundreds of pounds in those days. I got my 585 for £70 at a radio rally and it was much better than both of these scopes for the stuff I was doing

This difference in trace quality is almost certainly why I dislike the 2465 but the other reason is all the distracting lamp indicators and the fussy little cheapo controls on the user interface. The 485 looks a much nicer scope and if it can do a 300MHz BW and still have a trace quality better than a 465 then I would definitely choose this over the 2465.

[David Hess]

This whole archived discussion thread at the TekScopes email list is worth reading but start with this message:

https://groups.io/g/TekScopes/message/107383

The design teams deployed the new scopes and put them to use. In about two months, the engineering manager of GVG had collected all of the 7704s, put them on pallets and shipped them back to Tek Beaverton. The engineers gladly reverted to their trusted 547s.

Why? - Spot size.

[tggzzz]

The 485 looks a much nicer scope and if it can do a 300MHz BW and still have a trace quality better than a 465 then I would definitely choose this over the 2465.

Well I like the 485's display, e.g. 1ns/division:

[precaud]

The design teams deployed the new scopes and put them to use. In about two months, the engineering manager of GVG had collected all of the 7704s, put them on pallets and shipped them back to Tek Beaverton. The engineers gladly reverted to their trusted 547s.

Why? - Spot size.

The 547 was my fave scope ever. I got a near-perfect one that I used until 1996, then moved and put it, several backups, and other 500-series scopes in an outdoor storage shed, where they were to sit until I retired and would rebuild. Five years ago the shed was "cleaned out" by thieves over Thanksgiving weekend. The scopes never appeared in the local market for resale. Chances are they got dismantled and sold for scrap. Lots of aluminum in those...

[David Hess]

This is my 7904 displaying both rising and falling edges at two different sweep speeds.  The transient response needs a little bit of adjusting but I need a faster source among other things to do that.

The 547 was my fave scope ever. I got a near-perfect one that I used until 1996, then moved and put it, several backups, and other 500-series scopes in an outdoor storage shed, where they were to sit until I retired and would rebuild. Five years ago the shed was "cleaned out" by thieves over Thanksgiving weekend. The scopes never appeared in the local market for resale. Chances are they got dismantled and sold for scrap. Lots of aluminum in those...

That is a shame.  It would take a lot of work to steal a bunch of heavy 500 series oscilloscopes but I have heard of weirder things being stolen.

I picked up mine through Craigslist for $50 but I could understand not wanting  to hunt another down and shipping can be literally a pain.

[mtdoc]

I own a 465b, 475, 2236, and 2467. I’m partial to the 2467:

[rhb]

The 485 looks a much nicer scope and if it can do a 300MHz BW and still have a trace quality better than a 465 then I would definitely choose this over the 2465.

Well I like the 485's display, e.g. 1ns/division:

That's a proper step response.  I'll probably tweak mine for a little less overshoot.  But the 3% on the Instek  MSO-2204EA and the 7% on the Keysight MSOX3104T are ridiculous.  Especially the latter

[med6753]

The scopes with the sharpest and best defined traces IMHO are the old Tek 500 series. Nothing comes close.

The analog scopes in my collection are a 2465, 2465 DMS, 465, OS-245 (7603N), and a B&K 2120. The 2465 twins have the “fuzzy wuzzy” traces while the others have acceptable traces. I've never seen or used a 485 so I can't comment on it. It's been at least 30 years since I used a 475 but I don't recall the trace being “fuzzy”. My first experience with a 2465 was back in the early 1990's. I had just built a Heathkit IG-4244 Oscilloscope Calibrator and I wanted to test it's high frequency response. The only scope I had at that time was the 20MHz B&K 2120. So I asked an engineer at work if I could borrow his new 2465. All the measurement parameters came out dead nuts but the trace looked like crap. I thought the scope was broken. I mentioned this to the engineer and he said “Nope, they are like that”. It certainly didn't compare to the 7904's I had used in the past. It was a real disappointment.

Most of my hobbyist stuff is low frequency so unless I need the high frequency response I keep the 20MHz b/w limiter on. That really sharpens the trace on the 2465 twins. It was mentioned that they found the 2465 “too big” compared to the 465. I have to disagree with that. They are practically the same size. In fact, the 465 weighs considerably more than a 2465 due to it's linear power supply and big iron transformer.

Should an analog scope be processor controlled? Interesting question. I think Tek engineers decided to go that route so they could pack as many features and options in the available footprint and still have a portable scope. Of course that makes maintenance/repair so much more complicated and I'm painfully aware of that. But are the controls “fussy” and cheap feeling? I don't think so. I have no problem with the layout and I find it easy to use.     

[G0HZU]

It was mentioned that they found the 2465 “too big” compared to the 465. I have to disagree with that.

It was really a works specific gripe in that the 465 fitted our shelving system at work and the 2465 didn't. I think our shelves were a standard size/height so sig gens, scopes and various meters fitted. The 2465 might have fitted if I'd removed the handle and the stuff on top but I think I'd have been in trouble with the owner

At home I was using a Tek 585 which was enormous in comparison.

I haven't used one of these 2465 scopes for many years but I do vaguely remember that the owner of that first 2465 warned me in advance about the rocker selector for 50R/1meg/etc selection. This wasn't a very precise control and it was easy to flick it to the wrong setting. Looking at later models it looks like this control was changed and it was used in a few places on the front panel.

I still think it's worth trying both the 485 and 2465 to see which (if either) are OK for your needs. For me, the human factors of a scope are very important and a typical scope session involves lots of control tweaking and so the layout and ease of use are very important compared to other test gear. Also, the build quality has to be good so the controls don't wear out or fall off and obviously, the display trace quality and triggering have to be very good. Probably the best analogue scope I've used in this respect is the Iwatsu SS5710/1 although they are quite big scopes. The 485 looks quite good to me. For, me the 2465 failed these requirements in too many places and it's a scope I've avoided ever since.

[David Hess]

The 22xx and 24xx series oscilloscopes have slightly larger footprints than the 4xx series so Tektronix had to increase the size of their oscilloscope carts from the 200 (11.5x16.5), to the 200C (12.9x17.3), to the K212 (13.0x17.3).

[rhb]

My regular scope needs to be an MSO.  I'm expecting an R&S RTM3K demo unit at any minute.  The 485 will be there primarily for one purpose, to check for ringing on GPIO traces. Whether I go through with getting a 485 in part depends upon the R&S step response.  However, I should very much like to have a fast purely analog scope, and the 485 seems to be the best fit for what I want and the space required.  So even if not needed I expect I shall get one anyway.

I had an opportunity to get one or more 475s in need of repair, but in the end passed on them because I really didn't want to repair scopes.  However, I had occasion recently to look at my 465 manual and it is so beautifully written I had some pangs of regret on passing on the 475s.

[bd139]

The manual is a pleasure. I’ve restored a few, I think 11 off 465, 465B and 475.  It’s a rewarding experience with a great outcome. These were completely dead and one was rotting when they were obtained for pittance:

[David Hess]

The 485 will be there primarily for one purpose, to check for ringing on GPIO traces. Whether I go through with getting a 485 in part depends upon the R&S step response.

Unless the R&S RTM3K is broken, the only thing which will matter for that application is bandwidth.  A used analog oscilloscope has the advantage of much higher bandwidth for a given price versus a new DSO.

[Howardlong]

The manual is a pleasure. I’ve restored a few, I think 11 off 465, 465B and 475.  It’s a rewarding experience with a great outcome. These were completely dead and one was rotting when they were obtained for pittance:

The trace rotation’s off on the 475.  ;-)

[bd139]

Haha we spotted  . They were just chucked in a pile there. In theory you should alter trace rotation when you move the things.

[David Hess]

The first photograph is the bad transient response on the 465 I am refurbishing.  Initially the CRT trace was fuzzier but it improved after a couple hours of operation and cleaning the bandwidth switch.  I suspect this instrument spent years in storage.

The second photograph is the same transient response on my 2232 which is within specifications although the 2% overshoot is missing probably indicating that it was last calibrated with a poor source or the service manual instructions were not read carefully enough.  I did not think it worth recalibrating just for that.  Notice that the 2232 trace is cleaner than the 465 trace.

The third photograph is the PG506 fast rise output used in these tests on a 14GHz sampling oscilloscope.  Ignore the pattern dependent jitter; it was a deliberate part of the test.  It looks like the RG-400 patch cable I was using might be displaying dribble up but I did not notice it at the time or I would have confirmed it.

[G0HZU]

The 465 is at best average in terms of trace sharpness but it should look better than the photo above. My 465 was last serviced nearly 25 years ago when I first bought it. I did it all myself and did as much of the stuff in the manual that I could. I think mine is a reasonably good example although it was quite badly out of adjustment when I first got it. I think it took me a couple of days to wade through the procedures in the manual.

My trace response is quite similar to the 2232 image. However, I suspect that if you put both scopes side by side the 2232 would edge it on sharpness because it's hard to take photos of CRT traces and retain the sharpness. Also the setting of the intensity control and camera settings seem to significantly affect the results with a camera. None of my cameras seem to be able to capture the CRT display without making the scope trace look fuzzy. The risetime looks very droopy on the 465 and I guess you still have this to fix. It would be nice to see the response when it is fixed. I find that the quality/size of the 50R termination affects the response a bit and mine shows a bit of excess overshoot with a cheapo (long and big) BNC 50R feedthrough.

[particleman]

The first photograph is the bad transient response on the 465 I am refurbishing.  Initially the CRT trace was fuzzier but it improved after a couple hours of operation and cleaning the bandwidth switch.  I suspect this instrument spent years in storage.

The second photograph is the same transient response on my 2232 which is within specifications although the 2% overshoot is missing probably indicating that it was last calibrated with a poor source or the service manual instructions were not read carefully enough.  I did not think it worth recalibrating just for that.  Notice that the 2232 trace is cleaner than the 465 trace.

The third photograph is the PG506 fast rise output used in these tests on a 14GHz sampling oscilloscope.  Ignore the pattern dependent jitter; it was a deliberate part of the test.  It looks like the RG-400 patch cable I was using might be displaying dribble up but I did not notice it at the time or I would have confirmed it.

David, out of curiosity is the picture of the 465 trace also 200mV/division?

[David Hess]

The 465 is at best average in terms of trace sharpness but it should look better than the photo above.

Possibly and I do not have any experience with different 465s but others have said that they were not as sharp as later 100 MHz CRTs in the 22xx series and that there was considerable variation between early 465s and late 465Bs.  Mine might just be old or have a lot of hours although the CRT does not display double peaking.

My trace response is quite similar to the 2232 image. However, I suspect that if you put both scopes side by side the 2232 would edge it on sharpness because it's hard to take photos of CRT traces and retain the sharpness. Also the setting of the intensity control and camera settings seem to significantly affect the results with a camera. None of my cameras seem to be able to capture the CRT display without making the scope trace look fuzzy.

I picked up a Canon SX150 just for taking oscilloscope photographs.  It is much better than the piece of junk Sony DSC-S70 that I used to use.  I get better exposures with relatively high ambient light levels but this makes it difficult to prevent shadows.

The risetime looks very droopy on the 465 and I guess you still have this to fix. It would be nice to see the response when it is fixed. I find that the quality/size of the 50R termination affects the response a bit and mine shows a bit of excess overshoot with a cheapo (long and big) BNC 50R feedthrough.

It is the same configuration including 50 ohm feedthrough for both photographs but something is obviously wrong with the 465.  It was even worse before I started working with it and I still need to go through the vertical signal paths in detail.

David, out of curiosity is the picture of the 465 trace also 200mV/division?

Yes, I am pretty sure it is also 200mV/div with the variable control not engaged and the pulse output adjusted at the source for 1 volt deflection.  I did not take any specific notes but that is almost always what I start testing with unless there is a problem.

Ideally this test is first done at the native 5mV/div on a 465 where none of the high impedance attenuators or collector loads are used but I checked the vertical ranges and they all worked and produced results consistent with the 200mV/div result.

I am working on rebuilding the fan and power supply first.

[BravoV]

... because it's hard to take photos of CRT traces and retain the sharpness. Also the setting of the intensity control and camera settings seem to significantly affect the results with a camera. None of my cameras seem to be able to capture the CRT display without making the scope trace look fuzzy.

2565B shot using entry level DSLR with crappy stock lens.

Is this trace considered fuzzy compared to those sharper Tek 4xx series ?

[David Hess]

It looks fuzzy to me and like my 2445B.  The 20 MHz bandwidth limit should be used for consistent comparisons.

[BravoV]

It looks fuzzy to me and like my 2445B.  The 20 MHz bandwidth limit should be used for consistent comparisons.

Ok, I believe you, and you've just made my TEA disease getting worst. 

[rhb]

This has wandered a long way from my original question, which is OK.

I received an R&S RTM3K  on demo today and  t am absolutely awestruck.  The default response is a 2-3% overshoot with a 350 pS rise time.  But if I engage the math functions and apply a 1 GHz low pass filter I get a 450 pS rise time with *no* overshoot. The input is one of Leo Bodnar's 40 pS rise time pulsers. Mine measured at 36 pS when shipped a few months ago.

It is so good, I may well decide to not get a 485. The RTM3K was clearly specified by people who used scopes every day.  After the heartbreak of a bargain  MSOX3104T, it is a welcome sign that not all is lost.

Having said that I feel obliged to note that comparing my Keysight 33622A  to a GPSDO leaves me in great awe of the designers of the 33622A.   That comparison showed that instabilities relative to my 8648C with the high stability option were the 8648C.  I've not opened up the 33622A, but so far as i know it does not have the high stability option.